Using a prospective data base of 1561 patients who had surgery for benign biliary tract disease from May 1973 to February 1974 collected in a stratified random sample of 17 nonfederal hospitals, the proposed dissertation research intends to accomplish three primary objectives. One goal is to identify and investigate organizational characteristics of professional work which are associated with particular patterns of clinical decision-making. Diagnostic accuracy in evaluating non-malignant surgical disease of the biliary tract will be the domain of professional decision-making examined. The second objective of research is to investigate the relationship between diagnostic accuracy and surgical outcomes, attempting to identify certain patterns of diagnosis which are associated with improvements in quality of care delivered. Thirdly, an attempt will be made to model and test possible complex causal relationships between hospital/medical staff organizational arrangements, individual and aggregated physician characteristics, diagnostic accuracy and postsurgical morbidity, mortality and length of stay. Special emphasis wil be placed on examining how particular structural aspects of the hospital, i.e. 1) the control and coordination of the medical staff, and 2) the experience of the staff with comparable patients treated, impact the process of diagnostic accuracy, patient outcomes and length of stay.